package com.qiche.util;

/**
 * @author chendezhi
 * @date 2018/3/28 13:40
 *
 * 经纬度计算距离
 */
public class DistanceUtil {
    //赤道半径
    private static final  double EARTH_RADIUS = 6378137;
    private static double rad(double d){
        return d * Math.PI / 180.0;
    }

    /**
     *
     * @param lon1 经度
     * @param lat1 纬度
     * @param lon2 经度
     * @param lat2 纬度
     * @return 单位千米
     */
    public static double GetDistance(double lon1,double lat1,double lon2, double lat2) {
        double radLat1 = rad(lat1);
        double radLat2 = rad(lat2);
        double a = radLat1 - radLat2;
        double b = rad(lon1) - rad(lon2);
        double s = 2 *Math.asin(Math.sqrt(Math.pow(Math.sin(a/2),2)+Math.cos(radLat1)*Math.cos(radLat2)*Math.pow(Math.sin(b/2),2)));
        s = s * EARTH_RADIUS;
        //单位千米
        return s/1_000;
    }
}
